Overload devices are commonly used both in electrical and internal combustion motors, in electrical motors the overload devices being slow heating current sensors which deflect bi-metallic strips, or alternatively fuses or circuit breakers which change state upon sharp increase of current. Overload devices for internal combustion engines are more complex, and usually sense the fuel intake of the engines.
In both cases, overload conditions can exist which will result in a reduction of angular velocity of the rotor (which term includes crankshaft) and under some circumstances damage can be effected to the engine or motor without the overload devices functioning. Thus for example in the case of a vehicle engine, it is necessary for the fuel flow to be sufficient to supply short term high power requirements, and it is necessary for the overload condition to be sensed above that relatively large flow. In the case of an electric motor, a thermal overload device will not function to fully protect a motor under conditions of extreme cold, for example if the motor is operating under frosty or other very cold conditions.
In most instances however, both internal combustion motors and electric motors have overload conditions associated with loss of angular velocity, and the main object of this invention is to provide a safety device which is responsive to the reduction of angular velocity.